Brake actuating mechanisms are well known wherein fluid pressure may be applied to a piston to move the piston in conjunction with a spring force operatively associated between the piston and a brake. Conventionally, the brakes are released upon application of fluid pressure and are applied by the spring means associated with the brakes upon the release or loss of the fluid pressure. Such brake actuating mechanisms or systems have been used in a wide variety of applications from vehicle parking brakes to aerospace applications.
One of the problems in aerospace applications is that such brake actuators often are used with hydraulic motors, such as a wobbler-plate type hydraulic motor. These motors usually have a rather large, massive port structure, often called a "port plate", which have fluid ports to supply fluid to the hydraulic motor, such as to the pistons of a wobbler-plate type motor. The port structure is rather massive in order to avoid deflections at the interface with the motor block. The actuator piston often must be located outside or about the port structure in order to operate effectively with the spring means, brake disks and other components of the brake actuating mechanism. This creates a problem particularly in aerospace applications where space limitations are critical. In other words, envelope constraints often restrict the space available for packaging a required brake actuator mechanism.
A somewhat related problem with such applications is that all dynamic sealing locations leading to atmosphere are required to have double seals which further complicates the envelope problem.
Still another problem with brake actuators of the character described concerns hydraulic pressure spikes. In other words, where the application of fluid pressure is effective to allow the spring to apply a braking force, pressure spikes can cause problems in momentarily releasing and applying the braking forces.
This invention is directed to solving the above problems in a brake actuator for use in combination with a hydraulic motor.